postgres: fix precision for time columns in time series query mode

pkg/tsdb/postgres/postgres.go

@@ -7,7 +7,6 @@ import (
 	"math"
 	"net/url"
 	"strconv"
-	"time"
 
 	"github.com/go-xorm/core"
 	"github.com/grafana/grafana/pkg/components/null"
@@ -219,13 +218,16 @@ func (e PostgresQueryEndpoint) transformToTimeSeries(query *tsdb.Query, rows *co
 			return err
 		}
 
+		// converts column named time to unix timestamp in milliseconds to make
+		// native mysql datetime types and epoch dates work in
+		// annotation and table queries.
+		tsdb.ConvertSqlTimeColumnToEpochMs(values, timeIndex)
+
 		switch columnValue := values[timeIndex].(type) {
 		case int64:
-			timestamp = float64(columnValue * 1000)
+			timestamp = float64(columnValue)
 		case float64:
-			timestamp = columnValue * 1000
-		case time.Time:
-			timestamp = float64(columnValue.UnixNano() / 1e6)
+			timestamp = columnValue
 		default:
 			return fmt.Errorf("Invalid type for column time, must be of type timestamp or unix timestamp, got: %T %v", columnValue, columnValue)
 		}